Programmable quasi-direct space-to-time pulse shaper with active wavefront correction

Abstract

We experimentally demonstrate an extremely compact and programmable pulse shaper composed of a single phase mask encoded into a spatial light modulator. Its principle of operation is similar to the previously theoretically introduced quasi-direct space-to-time pulse shaper [Opt. Express 16, 16993 (2008)], which is based on diffractive optics. The proposed pulse shaper exhibits not only real-time temporal modulation, but also high-efficiency output pulses thanks to an active correction of the wavefront aberrations. © 2012 Optical Society of America OCIS codes: 320.5540, 050.1970, 220.1000 Today, femtosecond pulse shaping is a widespread technology. User-defined temporal waveforms with control of phase, amplitude, and polarization are required in many applications, such as high-field laser-matter interactions, photonic processing of telecom signals, and nonlinear microscopy. Pulse shaping is usually performed through a space-to-time transformation, where spatial masking of an optical beam causes its temporal modulation. In the Fourier-transform pulse shaping technique, the complex mask is placed at the Fourier plane of a zero-dispersion grating device where the optical frequency spectrum is spatially dispersed [1]. In a different approach, if a spatial mask is placed in the input plane of a generalized spectrometer, a direct (for a diffractive grating) or quasi-direct [for a diffractive lens (DL)] space-to-time mapping of the input spatial mask into the output temporal waveform is obtained. The advantages of these approaches are the compactness of the setups and the saving of time, as the Fouriertransform computation of the spatial patterns is not needed. In this context, the direct space-to-time (DST) [2] and the quasi-direct space-to-time (QDST) [3,4] pulse shapers have demonstrated their utility for highrepetition-rate wavelength-division-multiplexed systems [5], the generation of millimeter waves [6], the generation of fractal light pulses [7], and the study of molecular alignment [8], and also in the spectral domain to obtain bandpass optical filters [9,10].Compact, dynamic, user-friendly, and fast-operation devices demanded by nonexpert pulse-shaper users have inspired researchers to look for simple and compact designs. In this context, DST pulse shapers have been recently reduced to a phase-only spatial light modulator (SLM) together with a refractive lens to create a very innovative device [11]. However, high-power Ti:sapphire laser systems suffer from wavefront aberrations due to imperfections in the optical components, and pumpinduced thermal distortions in the amplifiers. Although thermal distortions can be reduced by cooling the Ti:sapphire crystal, an accurate correction of wavefront aberrations needs a more versatile approach usually based on adaptive optics [12,13].In this Letter, we show that the QDST pulse shaper can be reduced to a simple phase mask. As far as we know, this is the first proposal of a single diffractive element pulse shaper. In this proposal the entire size of the pulse shaper is...

Diffractive control of 3D multifilamentation in fused silica with micrometric resolution

“…On the other hand, the use of diffractive optics has demonstrated its capability to provide not only compact temporal pulse shapers [15], but also to manipulate nonlinear optical phenomena in the axial [16,17], as well as in the transversal direction of the pulse propagation [18]. In this context, we will focus on filamentation [19], which is basically a non-linear propagation phenomenon that is extended a distance longer than the Rayleigh range associated with the pulse.…”